This is a down-to-the-wire, bite-your-nails, what-about-the-rent? time for several million federal workers and military personnel and their paychecks. Because of a Capitol Hill budget crunch, Defense aides may get only half pay this Friday. HEW workers face the same half-a-loaf treatment when their money comes due Tuesday.

Locally more than 83,000 civilian employes of Defense (DOD) may get paid for only five days of work in this Friday's check, instead of the full two-week pay check. The Pentagon technically went broke as of Oct. 1.

Congressional failure to approve budgets for the new fiscal year also affects pay checks for military personnel (there are about 60,000 here) and for 145,000 HEW staffers, including 38,000 here and 20,000-plus in Baltimore. Energy, Labor and some other federal operations also are close to the financial wire in upcoming checks. Today will determine whether those employes get 50 cents on the dollar, or full checks.

Budgets, money bills and spending authorizations are in various stages of development in the House and Senate. Even veteran Capitol Hill staffers, who have lived through the penniless fiscal year foul-up before, are confused this year. HEW employes are especially nervous because many of them were temporarily short-changed on a pay day last year because of a similar crisis.

Normally Congress can put the money back in pay checks due during these budget mess times by approving a "continuing resolution." That authorizes agencies to keep spending at previous fiscal year levels until budgets can be formally approved.

The House has passed a continuing resolution that takes care of HEW, Labor, Defense and other agencies facing immediate money troubles. Yesterday the Senate Appropriations Committee cleared a similar resolution but without the Defense Department in it. It does, however, include the Energy Department, which the House resolution excludes. Idea is to put pressure on the Senate to approve the full budget, rather than just a continuing appropriation.

If the ploy fails, insiders believe that Senate-House conferees would accept a compromise version of the continuing resolution and allow payments to be made to all federal workers, including civilian and military personnel in Army, Navy and Air Force, as well as the Energy Department. But everybody is worried. Computers must be programmed on time and checks written. Much depends on politicking, and personal temperaments on Capitol Hill.

HEW Secretary Joseph Califano, taking advantage of his high standing in Washington's Old Boy network, has written a "Dear Maggie" letter to Senate Appropriations Committee Chairman Warren Magnuson (D-Wash.).

Califano spelled out the HEW problem, and has asked Magnuson and Majority Leader Robert Byrd (D-W. Va.) to call in their IOUs with various senators, so Califano and other department heads won't have to issue IOUs to employes.

If Congress approves the budgets, or continuing resolution, by the close of business today, most payrolls can be met. Defense has written two pay checks for each employe, each for one week's work.

If something happens to delay approval of the budget, most of the 83,000 DOD civilians here will get checks for only one week's work, for service performed between Sept. 24 and Oct. 1. Military personnel may be issued checks with instructions not to cash them until the Pentagon gets something in its checking account.

HEW employes in their upcoming pay day would get money for only one week unless the budget snarl is settled today. Energy Department workers face the same prospect.

Most people think all the pieces of the giant political jigsaw will come together today on time. A lot of innocent people out there - and their creditors - sincerely hope so.

Postal Strike Outlook: The possibility of even wildcat strikes in the Postal Service is fading rapidly. Members of the giant National Association of Letter Carriers have voted 127,588 to 21,206 in favor of ratifying the proposed contract. Members of the American Postal Workers Union are still balloting by mail. The Mailhandlers Union didn't send the contract out for ratification, since all parties in the negotiations agreed to binding arbitration in the second round of talks.

The contract calls for raises of about 21 percent over the next three years, with a link to the cost-of-living that could push the dollar value higher if inflation continues. In addition, all regular postal employes would be guaranteed lifetime protection from layoffs.

Chuck Merin has moved over to Health, Education and Welfare as intergovernmental liaison for the major study of social security coverage mandated by Congress. Merin has been legislative assistant with the National Association of Retired Federal Employes. The retiree group now has almost 300,000 dues-paying members.